Stabilizing with iodide an imagewise exposed photosensitive composition containing a halogenated photoactivator and an organic amine color former

ABSTRACT

A PHOTOGRAPHIC PRINT-OUT IMAGE OBTAINED BY EXPOSING TO ACTIVATING ELECTROMAGNETIC RADIATION A RECORDING ELEMENT COMPRISING A PHOTOSENSITIVE ORGANIC POLYHALOGEN COMPOUND RELEASING ON SUCH EXPOSURE A HALOGEN-CONTAINING FREE RADICAL INTO WORKING RELATIONSHIP WITH AN AMINE HAVING AN AROMATIC CHARACTER AND REACTIVE WITH THE PHOTOLYTICALLY PRODUCED FREE RADICAL TO FORM A DYE IS STABILIZED AGAINST DISCOLORATION BY TREATING THE REMAINING UNEXPOSED POLYHALOGEN COMPOUND WITH A COMPOUND CONTAINING IONICALLY BOUND IODINE.

United States Patent 3,708,297 STABILIZING WITH IODIDE AN lNlAGEWISEEXPOSED PHOTOSENSITIVE COMPOSITION CONTAINING A HALOGENATED PHOTO-ACTIVATOR AND AN ORGANIC AMINE COLOR FORMER Albert Lucien Poot, Koutich,and Edwin Hendrik Hazenbosch, Mechelen, Belgium, assignors toAgfa-Gevaert, Mortsel, Belgium No Drawing. Filed Oct. 8, 1970, Ser. No.79,283 Claims priority, application Great Britain, Oct. 9, 1969,49,685/69 Int. Cl. G03c 5/24 US. Cl. 9648 11 Claims ABSTRACT OF THEDISCLOSURE A photographic print-out image obtained by exposing toactivating electromagnetic radiation a recording element comprising aphotosensitive organic polyhalogen compound releasing on such exposure ahalogen-containing free radical into working relationship with'an aminehaving an aromatic character and reactive with the photolyticallyproduced free radical to form a dye isstabilized against discolorationby treating the remaining unexposed polyhalogen compound with a compoundcontaining ionically bound iodine.

A preferred photosensitive polyhalogen compound corresponds to thefollowing general formula:

wherein: Z represents the necessary atoms to close a benzene nucleus,and a preferred ionic iodine compound is an alkali metal iodide,alkaline earth metal iodide, or onium iodide.

The present invention relates to non-silver print-out photographicrecording and recording materials suited therefor.

It is well known that polyhalogen compounds, such as carbontetrabromide, are split into free-radical fragments on irradiation withultra-violet light.

A print-out photographic process based on a colour reaction produced byan exposure to ultraviolet light of a mixture of carbon tetrabromide anddiphenylamine and other secondary and tertiary arylamines has beendescribed in Phot. Sc. and Eng. 5, March-April 1961, pp. 98l03. By thefact that carbon tetrabromide is relatively volatile it is possible toobtain a fixed or stabilized image by heating the exposed recordingelement. The high volatility of the carbon tetrabromide impairs,however, the shelf life of the recording material so that it can alreadybe useless a few days after its manufacture.

Therefore it has been proposed to apply polyhalogenated aromatichydrocarbon or particular polyhalogenated heterocyclic compounds thathave a sufliciently high photosensitivity and by means of whichrecording layers with an improved shelf life are produced.

Because of the rather low vapour pressure of said compounds the completestabilization of the obtained image is often difficult to realize orrequires relatively high temperatures and a rather long heat treatment.

It is the main object of the present invention to provide astabilization technique that is not based on the volatility of thephotosensitive organic polyhalogen compounds and that offers thepossibility to produce photosensitive printout recording materialshaving an improved shelf life, high photosensitivtiy and good imagestabilization properties.

3,708,297 Patented Jan. 2, 1973 A method has now been found of recordingand stabilizing a photographic print-out image containing the steps of:

(1) Exposing a recording material to activating electromagneticradiation, said recording material containing a recording elementcomprising a photosensitive organic polyhalogen compound generating onexposure to active electormagnetic radiation a halogen-containing freeradical, said polyhalogen organic compound during exposure being inworking relationship with an amine having an aromatic character, andbeing capable of forming a dye by reaction with a photolyticallyproduced free radical generated by the photographically exposed organicpolyhalogen compound; and

(2) Treating the remaining unexposed organic polyhalogen compound with acompound that contains ionical- 1y bound iodine, and preferablysimultaneously applying heat to accelerate the stabilization reactionpreventing thereby darkening of the image background on a subsequentoverall ultraviolet light exposure.

By the term in working relationship has to be understood, that thehalogen-containing free radicals produced on exposure can come ineffective contact with a properly selected aromatic amine. The ioniciodine compound(s), however, when present in the recording material has(have) to be kept (at room temperature (20 C.)) away from directchemically reactive contact (i.e., to be kept in nonworkingrelationship) with respect to said organic polyhalogen compound beforeand preferably also during exposure, for it has been experienced thatotherwise a reduction in photosensitivity takes place especially whenaromatic amines being free from a N-vinyl group are used.

Preferred organic polyhalogen compounds are within the scope of thefollowing general formula:

R-CX wherein R is hydrogen, chlorine, bromine or iodine, an aliphaticradical including a substtiuted aliphatic radical, e.g. a substituted orunsubstituted alkyl radical, or an aromatic hydrocarbon radicalincluding a substituted aromatic hydrocarbon radical e.g. a phenylradical, a heterocyclic radical, a substituted heterocyclic radical, anacyl group, including a car'boxylic acid acyl group, a sulphonic acidacyl group and a sulphinic acid acyl group, a carboxyl group, acarboxylic acid ester group, an amide group or an aldehyde group, and

each of X is chlorine, bromine or iodine.

Particularly suited organic polyhalogen compounds are:

carbon tetrabromide, bromoform, iodoform, chloroform,fl-tribromoethanol, trichlorobromomethane, hexabromoethane,bromodichloromethane, pentachloroethane, methyl trichloroacetate, ethyltribromoacetate,

tribromoaceta-mide, tribromoacetaldehyde, tribromomethylbenzene,p-nitrotribromomethylbenzene, hexachloroethane, pentabromoethane,tetrabromobutane, hexachlorobenzene, tetrachlorotetrahydronaphthalene,a,a,a-tribromoacetophenone, 4-bromo-u,-m,a-tribromoacetophenone,3-nitro-a,a,a-tribromoacetophenone, 4-nitro-m,a,u-tribromoacetophenone,2-tribromomethylquinoline, 2-tribromomethyl-8-nitro-quinoline,2-tribromomethylquinoxaline,

2,3hexabromodimethylquinoxaline, chloro-2-tribromomethylquinoxaline Eachof these compounds is a halogenated organic compound in which the carbonatom substituted with more than one halogen atom carries no more thanone hydrogen atom.

Organic polyhalogen compounds preferred for their property to yield arecording material with particularly high shelf life and goodphotosensitivity and stabilizability correspond to the following generalformula:

Z represents the necessary atoms to close a benzene nucleus orsubstituted benzene nucleus e.g. carrying one or more substituents ofthe group of alkyl, alkoxy, halogen and nitro.

In order to illustrate the preparation of such photosensitive compoundsreference is made to the preparation receipt of2-tribromomethylquinoxaline (J. Chem. :Soc. 1928, 1974). The brominationis preferably carried out according to the following procedure:

A mixture of 330 g. of sodium acetate, 660 g. of acetic acid and 0.64mole of a Z-methylquinoxaline, is heated till the temperature reaches 70C. Whilst thoroughly stirring at that temperature 315 g. (1.9 mole) ofbromine dissolved in 600 ml. of acetic acid are added in a period oftime of 75 min. Thereupon the reaction mixture is boiled for 5 hr.,subsequently cooled down on a waterbath, and finally poured into water.The formed precipitate is filtered by suction and washed with water.

2-tribromomethylquinoxaline can be easily recrystallized from ethanoland melts at 112 C.

Suitable amines having an aromatic character and that are used inworking relationship with the photosensitive organic polyhalogencompound include primary, secondary and tertiary aromatic amines, e.g.the amines corresponding to the following general formula:

wherein:

R represents an alkyl group, e.g. a C -C alkyl group, an aralkyl group,e.g. a benzyl group, a hydroxyalkyl group, e.g. a hydroxyethyl group, ora sulphoalkyl group, e.g. a C -C sulphoalkyl group,

Z represents the necessary atoms to close a ring or ring system havingan aromatic character including such ring or ring system in substitutedform, e.g. a benzene ring or a naphthalene ring and such ringssubstituted e.g. with halogen, an alkyl group, an amino group orsubstituted amino group,

L represents a bivalent organic radical capable to link two amino groupstogether e.g. an alkylene or substituted alkylene radical, or organicradical containing alkylene groups, e.g. methylene groups interrupted byan aromatic radical, e.g. by a phenylene group or by hetero atoms, e.g.oxygen, or a bivalent amino group or substituted bivalent amino group,e.g. a

' group, a CH -O-CH group or 3.

.il l.

group wherein R represents hydrogen, an alkyl group,

a substituted alkyl group or an aralkyl group.

4 A particularly suited amine falling within the scope of said generalformula is N,'N-dipheny1-N,N-diethylethylenediamine.

Other particularly suited aromatic amines are:

arylamines e.g. diphenylamine, dibenzylamine, triphenylamine,N,N-diethylam'1ine, N,N-dimethylaniline, N-hydroxyethyl-N-ethylaniline,o-amino-diphenylamine, p-hydroxydiphenylamine, a-naphthylamine, p-aminoN-diethylaniline, p-aminodiphenyl, Z-aminodiphenyl,p-aminodiphenylamine, N-benzylaniline, lN-butylaniline,N-sec.butylaniline, 2,4-dia-mino diphenylamine,N,N-dibenzylethylenediamine, 2,6-di-tert.butylamine,a-dimethylamino-p-cresol, 3,4-dichloroaniline, m-N-diethylaminophenol,N-diethylaminotoluene, 'N,N-diphenylethylenediamine,diphenyl-p-phenylenediamine, p-dimethylaminobenzaldehyde, o-(dimethylaminomethyl -phenol, m-dimethylaminophenol,N,N'-dimethyl-a-naphthylamino, di-B-naphthylamine,di-fi-naphthyl-p-phenylenediamine, di-n-propylaniline, N-ethylaniline,N,N-benzylethylaniline, N-ethyl-N-phenylethanolamine,N-(2-ethylhexyl)-aniline, N-ethyl-o-toluidine, N-ethyl-m-toluidine,2-phenylaminoethanol, N-phenyl-cyclohexylarnine,phenyl-u-naphthyla-mine, phenyl-fi-naphthylamine,3-hydroxy-diphenylamine, N-methylaniline,IN-(a-methylbenzyl)-diethanolamine, N- a-methylbenzyl) -ethanolamine,N-methyl-o-toluidine, p-tolyl-u-naphthylamine, N-butyl-N-w-amino aceticacid propylaniline, N-ethylN-w-sulphonic acid butylaniline,3,S-diethyl-N-n-hexadecylaniline, 3,S-di-tert.butyl-N,N-dimethylaniline, 3,5-dimethyl-N,nhexadecylaniline,N-n-hexadecylaniline, -N,N-ethyl-octylaniline,N,N-ethyl-n-hexadecylaniline, N,N-ethyl-p-toluene-sulphonylaniline,N,N-ethyl-dodecylaniline, [t- (N -ethyl-anilino)ethyl carbanilate andheterocyclic amino compounds such as indoline, 1,2,3- trimethylindole,Z-aminobenzimidazole, 3-phenylindole, a-diethylaminopyridine,N-ethylcarbazole or 1,2-dihydro- 2,2,4-trimethylquinoline.

Aromatic amines containing a N-vinyl group yield much fog and thereforeare of no particular practical value for use in the process of thepresent invention. Suitable ionic iodine compounds are water-solubleiodides. Image stabilization is preferably carried out by means ofalkali metal iodides, alkaline earth metal iodides and onium iodides,e.g. sodium iodide, potassium iodide, organic and inorganic ammoniumiodides and barium iodide. Organic onium iodides are described moreparticularly in the published United Kingdom patent application1,151,363 filed Apr. 30, 1965, by Gevaert-Agfa N.V. which for that parthas to be read in conjunction herewith.

In order to prevent a premature reduction of the photosensitivity of thephotosensitive colour-producing system consisting of a photolyticallyfree radical-producing organic polyhalogen compound (photoactivator) andan aromatic amine (dye modificator) the ionic iodine compound isincorporated according to a first embodiment into the recording materialin such a way that direct chemically reactive contact with thephotosensitive polyhalogenated organic compound is prevented at roomtemperature (20 C.).

According to a secorid embodiment the ionic iodine compound isincorporated into the recording material in a stage following theinformation-wise exposure to activating electromagnetic radiation.

According to a preferred embodiment the ionic iodine compound is appliedfrom a liquid (solvent, solvent mixture or dispersing medium), whereinthe photosensitive organic polyhalogen compound is not soluble, whereasthe latter is applied from a liquid wherein the ionic iodine compound isnot soluble.

When producing the recording material by starting from an aqueous phaseand a hydrophobic phase, the ionic iodine compound is preferably appliedfrom the aqueous phase and the photosensitive organic polyhalogencompound together with the aromatic amine compound from the hydrophobicor lipophilic phase.

When using binding agents for one or both of said compounds preferably amore hydrophobic binding agent is used for the photoactivator and dyemodificator than is used for the ionic iodine compound.

According to a special embodiment the photo-sensitive organicpolyhalogen compound is present in a thermoplastic hydrophobic binderlayer, whereas the ionic iodine compound is present in a hydrophilicbinder layer, the binder of the hydrophobic layer being selected in sucha way that on melting it can penetrate in the hydrophilic binder layer.For thermosensitive materials containing such binders in separate layersreference is made to the French patent specification 1,531,440 filedApr. 3, 1967 by Gevaert-Agfa N.V.

According to another special embodiment the photosensitive organicpolyhalogen compound and the ionic iodine compound are applied in amixture of two binding agents one of which contains the organicpolyhalogen compound and the other the ionic iodine compound. Saidbinding agents are selected in such a way that they are not compatibleat room temperature, so that one of them at this temperature is presentin the form of dispersed particles in the continuous phase of the otherbinding agent, which forms a homogeneous mixture with the dispersedbinding agent by melting.

For such type of binding agents reference is made to the United Statespjatent specification 3,223,838 of Shoishiro Hoshino and Akira Kato,issued Dec. 14, 1965.

According to still another embodiment one or both of said compounds areencapsulated or separated from each other by means of a meltable layer,e.g. a hydrophobic thermoplastic polymer layer or wax layer. Suitableencapsulating techniques for aqueous media are described in the UnitedKingdom patent specifications 1,048,696 and 1,048,697 both filed July10, 1963, by Gevaert-Photo- Producten N.V.

Further, the ionic iodine compound can be applied in a poroushydrophilic support, e.g. paper, by imbibition and the photosensitivecompound applied thereto in a meltable hydrophobic binding agent. Thecontact of the ionic iodine compound with the organic photosensitivecompound may be improved by hygroscopic compounds, e.g. glycerol, thatcome at the disposal of both compounds at the right moment after thephotographic exposure. Glycerol and the ionic iodine compound can beencapsulated according to the technique described in the Belgian patentspecification 741,954 filed Apr. 3, 1967, by Gevaert-Agfa N.V.(corresponding with United Kingdom patent applications 55,080/68 filedNov. 20, 1968 and 2,229/69 filed Dec. 31, 1968, both by Gevaert- AgfaN.V.). The capsules can release their contents by rupture (pressuretreatment) or melting of the capsule wall (heat treatment). Although acompletely dry stabilization is preferred the present invention does notexclude the use of ionic iodide-producing compounds present in atreating liquid applied after the photographic exposure. A semi-wetstabilization may be carried out by means of a stabilizing liquidcomprised in a container or pod that can be ruptured and releases itscontents upon advancing the photosensitive element and sheetlikecontainer material between a pair of pressure rollers.

Suitable binding agents for the photosensitive organic polyhalogencompounds are hydrophobic hermoplastic binding agents e.g.acetylcellulose, having an acylation degree of preferably at least 2,cellulose acetate-butyrate, ethylcellulose (DS ethoxy preferably atleast 2), hydrophobic vinyl polymer and copolymers, e.g. polyvinylchloride, polyvinylidene chloride, polyvinyl acetate, alkylpolyacrylates, alkyl polymethacrylates, and polystyrene.

Optionally a plasticizer is used in admixture with the binder. Suitableplasticizers include tricresyl phosphate, tri(2-ethylhexyl) phosphate,dioctyl phthalate, di(2-ethylhexyl) tetrahydrophthalate,di(2-ehtylhexyl) maleate and polyethylene glycol.

The spectral sensitivity of the photosensitive print-out systemcontaining a normally, only U.V.-sensitive organic polyhalogen compoundand an aromatic amine can be extended. So, the inherent photosensitivityof Z-tribromomethyl-quinoxaline being in the spectral range of 300 to450 nm. can be extended to include a part of the visible spectrum bymeans of azocompounds as described in the United States patentspecification 3,042,516 of Eugene Wainer, issued July 3, 1962.

Particularly suited for that purpose are, e.g., the yellowN,N-dimethylphenylazoaniline and 4-phenylazodiphenylamine. Theseazocompounds are used in rather small amounts so that a heavy backgroundcolouration is excluded.

Other suitable spectral sensitizing agents are found in the class ofspectral sensitizing agents for light-sensitive silver halide andphotoconductive zinc oxide, e.g. in the class of the acridine dyes,cyanine dyes and styryl dyes, e.g. cyanine dyes and styryl dyesdescribed in the United Kingdom patent specification 1,000,195 filedApr. 2, 1962 by Horizons Inc., thiazine dyes and xanthene dyes, e.g.phthaleine dyes. In that respect have to be mentioned par ticularlyacridine orange, acridine red, rose bengale, methylene blue, pinacyanoland pinacryptol yellow.

In order to give an idea of the proportion of the different ingredientsin preferred photosensitive coating compositions the following list ofingredients expressed in parts by weight is presented:

Parts Solvent 1000 Film forming binding agent 10-50 Photosensitiveorganic polyhalogen compound 5-30 Aromatic amine 20-50 Spectralsensitizing agent 1-5 Said compositions may be coated onto a suitablesupport, e.g. a paper or resin support, according to any coatingtechnique known in the art.

As already mentioned the stabilization of the obtained image preferablyproceeds in dry state and with the aid of heat. Heat can be supplied tothe photographically exposed recording material by an infrared lamp orby contact with a hot body, e.g. by conveying it between a pair of hotrollers having a surface temperature of C.

In order to obtain a particularly clean image background the ioniciodine compounds are preferably combined with a hydrogen sulphite orhydrogen sulphitegenerating compound that can produce sulphur dioxide inacid medium.

Especially good results are obtained by means of a mixture of sodiumhydrogen sulphite or sodium disulphite (Na S O and sodium iodide.

Ionic iodine compound Solvent To a baryta-coated paper support asolution of the following stabilizing composition was applied in a ratioof 40 ml. per sq. rn.:

Sodium iodide g 1 Sodium hydrogen sulphite g 1 Propanol ml 20 Water ml80 After drying, a photosensitive coating composition containing thefollowing ingredients was coated theeron in a ratio of 40 ml. per sq.rn.:

2-tribromomethylquinoxaline g 5 Diphenylamine g Polystyrene g 2Chloroform ml 100 The recording material was dried and contact-exposedfor 10 sec. through a line transparency in a diazocopying apparatusActina S (trade name of Regrna N.V., Brussels, Belgium). The exposuresource was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm.from the photosensitive material. An intense green negative image of theoriginal was obtained on a light yellow background. The exposedrecording material was conveyed between a pair of hot rollers having asurface temperature of 150 C. Thereby the image colour turned to intensegrey-violet and the image background colour remained unchanged evenafter an intense exposure to ultraviolet light.

EXAMPLE 2 To a glassine type paper support having been precoated with astabilizing composition as described in Example 1, a photosensitivecoating composition containing the following ingredients was applied ina ratio of 40 ml. per

sq. rn.:

2-tribromomethylquinoxaline g 2 N,N-ethyl-fl-hydroxyethylaniline g 2Cellulose acetate-butyrate (type half second butyrate of Eastman,Kingsport, Tenn., U.S.A.DS Butyryl 1.7-DS acetyl 1.0-viscosity of a byweight solution in acetone at C.:48 cp.) g 2 Acetone l 100 The recordingmaterial was dried and contact-exposed for 6 see. through a linetransparency in an Actina S (trade name) diazocopying apparatus. Theexposure source was a 1000 W. mercury vapour bulb arranged at a distanceof 5 cm. from the photosensitive material. An intense green negativeimage of the original on a light yellow background was obtained. Astabilized image was obtained in the exposed recording material byconveying it between a pair of hot rollers having a surface temperatureof 125 C. The stabilized image had an intense violet colour and theslightly yellow image background did not darken even by a strongexposure to ultraviolet rays.

EXAMPLE 3 To a baryta-coated paper precoated With a stabilizingcomposition as described in Example 1 a photosensitive coatingcomposition containing the following ingredients was applied at a rateof 40 ml. per sq. 111.:

2-tribromomethylquinoxaline g 2 fl-(N-ethylanilino)-ethyl carbanilate g3 Cellulose acetate-butyrate (as in Example 2) g 3 Acetone ml 100 Therecording material was dried and contact-exposed for 6 see. through aline transparency in an Actina S (trade name) diazo copying apparatus.The exposure source was a 1000 w. mercury vapour bulb arranged at adistance of 5 cm. from the recording material. An intense green imagewas obtained. An intense purplish black stabilized image was obtained inthe exposed recording material by leading it between a pair of hotrollers having a surface temperature of 125 C.

EXAMPLE 4 To a baryta-coated paper precoated with a stabilizingcomposition as described in Example 1, a photosensitive coatingcomposition containing the following ingredients was applied in a ratioof 40 ml. per sq. m.:

2-tribromomethylquinoxaline g 5 N-vinylcarbazole g 5 Celluloseacetate-butyrate (see Example 2) g 5 Acetone ml 100 The recordingmaterial was dried and contact-exposed for 10 see. through a linetransparency in an Actina S (trade name) diazo'copying apparatus. Theexposure source 'was a 1000 w. mercury vapour bulb arranged at adistance of 5 cm. from the recording material. A yellowish-brownnegative image of the original was obtained. A stabilized image wasobtained by leading the recording material between a pair of hot rollersthe surface temperature of which was 125 C. The stabilized image had anintense brown colour.

EXAMPLE 5 On a polyethylene terephthalate film support a photosensitivelayer was coated in a ratio of 40 ml. per sq. m. from the followingcomposition:

2-tribromomethylquinoxaline g 8 N-ethyl-N-fi-hydroxyethylaniline g 8Cellulose acetate-butyrate (see Example 2) g 2 Acetone ml 100 Afterdrying of the photosensitive layer, a top-coat for image-stabilizingpurposes was applied thereto in a ratio of 40 ml. per sq. m. from asolution having the following composition:

Sodium iodide g 0.6 Sodium hydrogen sulphite g 1 Water ml Propanol ml 20After drying, the recording material was contact-exposed for 20 sec.through a line transparency in an Actina S (trade name) diazo copyingapparatus. The exposure source was a 1000 w. mercury vapour bulbarranged at a distance of 5 cm. from the recording material. An intensegreen negative image of the original was obtained. A stabilized imagewas obtained by conveying the exposed recording material between a pairof hot rollers the surface temperature of which was 110 C. Thestabilized image had an intense greyish violet colour and the imagebackground remained clear even after a strong exposure to ultravioletrays or an exposure to daylight for several days. If said stabilizingtreatment was not carried out the image background turned green to greyafter a few minutes exposure to daylight.

EXAMPLE 6 To a baryta-coated paper support a solution of the followingstabilizing composition was applied in a ratio of 40 ml. per sq. rn.:

Sodium iodide mg 600 Sodium disulphite mg 600 Water ml Propyl alcoholN-ethyl-N-B-hydroxyethylaniline mg 100 Exposure and heating forinitiating and accelerating the stabilization were efiected as describedin Example 1. A stable negative green print of the original wasobtained.

EXAMPLE 7 To a baryta-coated paper support a stabilizing composition asdescribed in Example 6 was applied.

On the dry stabilizing coating a photosensitive coating compositioncontaining the following ingredients was coated in a ratio of 40 ml. persq. m.:

N-ethyl-N-B-hydroxyethylaniline mg 100 2-tribromomethylquinoline mg 100Cellulose acetatebutyrate (see Example 2) mg 50 Acetone ml 5 Theexposure and heating for initiating and accelerating the stabilizationwere carried out as described in Example l. A stable violet-graynegative print-out image of the original was obtained.

EXAMPLE 8 To a bartya-coated paper support a stabilizing composition asdescribed in Example 6 was applied.

On the dry stabilizing coating a photosensitive coating compositioncontaining the following ingredients was Exposure and heating forinitiating and accelerating the stabilization were carried out asdescribed in Example 1. A stable blue negative print-out image of theoriginal was obtained.

EXAMPLE 9 To a baryta-coated paper support a solution of the followingstabilizing composition was applied in a ratio of 40 ml. per sq. m.:

Sodium iodide g-.. 1 Sodium hydrogen sulphite g 2 Propanol ml 20 Waterml 80 After drying, a photosensitive coating composition containing thefollowing ingredients was coated thereon in a ratio of 40 ml. per sq.m.:

2 tribromomethylquinoxaline g 5 l,2-dihydro-2,2,4-trimethylquinolineg..- 10 Cellulose acetate-butyrate (see Example 2) g 2 Methyl ethylketone ml 100 The recording material was dried and contact-exposed for 5sec. through a line transparency in a diazocopying apparatus Actina S(trade name). The exposure source was a 1000 w. mercury vapour bulbarranged at a distance of 5 cm. from the photosensitive material. Anintense brown negative image of the original was obtained on a lightyellow background. The exposed recording material was conveyed between apair of hot rollers having a surface temperature of 150 C. Thereby theimage colour turned to intense greyish black and the image backgroundcolour remained almost unchanged even after an intense exposure toultraviolet light.

EXAMPLE 10 To a glassine type paper support having been precoated with astabilizing composition as described in Example 2, a photosensitivecoating composition containing the following ingredients was applied ina ratio of 40 ml. per sq. m.:

10 2-tribromomethylquinoxaline g 5N,N'-diphenyl-N,N'-diethylethylenediamine g 5 Cellulose acetate-butyrate(see Example 2) g 2 Acetone l The recording material was dried andcontact-exposed for 6 sec. through a line transparency in an Actina S(trade name) diazocopying apparatus. The exposure source was a 1000 w.mercury vapour bulb arranged at a distance of 5 cm. from thephotosensitive material. An intense green negative image of the originalon a light yellow background was obtained. A stabilized image wasobtained in the exposed recording material by conveying it between apair of hot rollers having a surface temperature of C. The stabilizedimage had an intense brown colour and the slightly yellow imagebackground did not darken even by a strong exposure to ultraviolet rays.

We claim:

1. A method of forming and stabilizing a photographic print-out imagecontaining the steps of:

(1) imagewise exposing to activating electromagnetic radiation, arecording material containing a recording element comprising aphotosensitive organic polyhalogen compound generating on exposure toactivating electromagnetic radiation a halogen-containing free radicaland in working relation with said polyhalogen compound during exposurean amine free of N-vinyl groups having an aromatic character capable offorming a dye image in the exposed areas by reaction with aphotolytically produced free radical generated by the photographicallyexposed organic polyhalogen compound, and

(2) after said exposure contacting the remaining unexposed polyhalogencompound with a water-soluble inorganic or organic iodide to stabilizethe unexposed areas of said material against color change upon exposureto light.

2. A method according to claim 1, wherein the iodide is present in therecording material in isolated relation preventing direct chemicallyreactive contact with the photosensitive organic polyhalogen compound atroom temperature and is brought into contact with said polyhalogencompound by heating the recording material after the exposure.

3. A method according to claim 1, wherein the iodide and photosensitivepolyhalogen compound are present in the recording material in twoseparate and distinct coatmgs.

4. A method according to claim 3, wherein the iodide and photosensitiveorganic polyhalogen compound are coated from different liquids that arenot miscible with each other.

5. A method according to claim 1, wherein the recording material afterits image-wise exposure is treated with a liquid containing awater-soluble iodide.

6. A method according to claim 1, wherein the photosensitive organicpolyhalogen compound is a compound of the following general formula:

R--CX wherein:

R is hydrogen, chlorine, bromine or iodine, an aliphatic group, anaromatic hydrocarbon group, a heterocyclic group, an acyl group, acarboxylic acid ester group, an amide group or an aldehyde group, andeach of X is chlorine, bromine or iodine. 7. A method according to claim1, wherein the photosensitive polyhalogen compound corresponds to thefollowing general formula:

vNs

wherein:

R represents an alkyl group, or an aralkyl group,

Z represents the necessary atoms to close a ring or ring system havingaromatic character, and

L represents a bivalent organic radical linking two amino groups.

9. A method according to claim 1, wherein the iodide is an alkali metaliodide, alkaline earth metal iodide or onium iodide.

10. A recording material according to claim 2, wherein the iodide insaid isolated relation is in admixture with hydrogen sulphite or with ahydrogen sulphite-generating compound.

11. A recording material according to claim 1, wherein the recordingmaterial contains a spectrally sensitizing agent selected from the classof azo dyes, acridine dyes,

12 cyanine dyes, styryl dyes, xanthene dyes, phthaleine dyes, andthiazine dyes.

References Cited UNITED STATES PATENTS 3,565,628 2/1971 Garland 96-903,512,976 5/1970 Yamada et al. 96-90 X 3,042,516 7/ 1962 Wainer 96-483,527,639 9/1970 Moraw 96-90 3,042,518 7/1962 Wainer 96-90 X FOREIGNPATENTS 916,779 1/1963 Great Britain 96-90 957,192 5/1964 Great Britain96-90 OTHER REFERENCES J. Chem. Soc. 1928, p. 1974.

NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant ExaminerUS. Cl. X.R. 96-90

